1. Field of the Invention
The present invention relates generally to medical systems and methods for treatment. More particularly, the present invention relates to apparatus and methods for treating aneurysms.
Aneurysms are enlargements or “bulges” in blood vessels which are often prone to rupture and which therefore present a serious risk to the patient. Aneurysms may occur in any blood vessel but are of particular concern when they occur in the cerebral vasculature or the patient's aorta.
The present invention is particularly concerned with aneurysms occurring in the aorta, particularly those referred to as aortic aneurysms. Abdominal aortic aneurysms (AAA's) are classified based on their location within the aorta as well as their shape and complexity. Aneurysms which are found below the renal arteries are referred to as infrarenal abdominal aortic aneurysms. Suprarenal abdominal aortic aneurysms occur above the renal arteries, while thoracic aortic aneurysms (TAA's) occur in the ascending, transverse, or descending part of the upper aorta.
Infrarenal aneurysms are the most common, representing about eighty percent (80%) of all aortic aneurysms. Suprarenal aneurysms are less common, representing about 20% of the aortic aneurysms. Thoracic aortic aneurysms are the least common and often the most difficult to treat.
The most common form of aneurysm is “fusiform,” where the enlargement extends about the entire aortic circumference. Less commonly, the aneurysms may be characterized by a bulge on one side of the blood vessel attached at a narrow neck. Thoracic aortic aneurysms are often dissecting aneurysms caused by hemorrhagic separation in the aortic wall, usually within the medial layer. The most common treatment for each of these types and forms of aneurysm is open surgical repair. Open surgical repair is quite successful in patients who are otherwise reasonably healthy and free from significant co-morbidities. Such open surgical procedures may be problematic, however, since access to the abdominal and thoracic aortas is difficult to obtain and because the aorta must be clamped off, placing significant strain on the patient's heart.
Over the past decade, endoluminal grafts have come into widespread use for the treatment of aortic aneurysm in patients who cannot undergo open surgical procedures. In general, endoluminal repairs access the aneurysm “endoluminally” through either or both iliac arteries in the groin. The grafts, which typically have been fabric or membrane tubes supported and attached by various stent structures, are then implanted, typically requiring several pieces or modules to be assembled in situ. Successful endoluminal procedures have a much shorter recovery period than open surgical procedures.
Present endoluminal aortic aneurysm repairs, however, suffer from a number of limitations. For example, a significant number of endoluminal repair patients experience leakage at the proximal juncture (attachment point closest to the heart) within two years of the initial repair procedure. While such leaks can often be fixed by further endoluminal procedures, the need to have such follow-up treatments significantly increases cost and is certainly undesirable for the patient. A less common but more serious problem has been graft migration. In instances where the graft migrates or slips from its intended position, open surgical repair is required. This is a particular problem since the patients receiving the endoluminal grafts are often those who are not considered to be good surgical candidates.
Further shortcomings of the present endoluminal graft systems relate to both deployment and configuration. For example, many of the commercially available endovascular systems are too large (above 12 F) for percutaneous introduction. Moreover, current devices often have an annular support frame that is stiff and difficult to deliver as well as unsuitable for treating many geometrically complex aneurysms, particularly infrarenal aneurysms with little space between the renal arteries and the upper end of the aneurysm, referred to as short-neck or no-neck aneurysms. Aneurysms having torturous geometries, are also difficult to treat.
In order to overcome some of the aforementioned challenges, the use of endograft systems having a scaffold structure and a filling structure has been proposed, such as in U.S. patent application Ser. No. 11/413,460 filed Apr. 28, 2006, the entire contents of which are incorporated herein by reference. These systems utilize a filling structure to help seal off and fill the aneurismal sac while creating a lumen for blood to traverse the aneurysm. Several references disclosing filling structures and which are the subject of the commonly owned, copending applications are described below. These systems may also include a stent-like scaffold which helps support the filling structure thereby further defining the lumen for blood flow. The filling structure may require a pre-filling step to help unfurl the filling structure prior to filling it with the hardenable filling material and an expandable balloon often is used to help support the endograft during filling and during hardening in order to ensure proper formation of a lumen for blood flow. Because the filling material may take some time to harden, the expanded balloon can occlude flow for an undesirable time. Additionally, even after filling and hardening of filling material in the filling structure, the aneurismal sac may not be completely sealed off and blood can still flow into the sac. For these reasons it would be desirable to provide alternative apparatus and methods that create a better seal between the aneurismal sac and the endograft. It would also be desirable to provide apparatus and methods that help filling structures expand and conform to the aneurysm anatomy. Moreover, it would also be desirable for sealing apparatus and methods to minimize or eliminate the need for a separate unfurling step as well as minimizing the need to use an inflated balloon for support during filling and hardening that can obstruct blood flow. It would also be desirable that the alternative apparatus have a low profile for ease of delivery and percutaneous introduction as well as flexibility to allow advancement of the device through torturous vessels such as the iliac arteries. It would further be desirable that such devices can accommodate a variety of different vessel and aneurysm anatomies. At least some of these objectives will be met by the inventions described hereinbelow.
2. Description of the Background Art
U.S. Patent Publication No. 2006/0025853 describes a double-walled filling structure for treating aortic and other aneurysms. Copending, commonly owned U.S. Patent Publication No. 2006/0212112, describes the use of liners and extenders to anchor and seal such double-walled filling structures within the aorta. The full disclosures of both these publications are incorporated herein by reference. PCT Publication No. WO 01/21108 describes expandable implants attached to a central graft for filling aortic aneurysms. See also U.S. Pat. Nos. 5,330,528; 5,534,024; 5,843,160; 6,168,592; 6,190,402; 6,312,462; 6,312,463; U.S. Patent Publications 2002/0045848; 2003/0014075; 2004/0204755; 2005/0004660; and PCT Publication No. WO 02/102282.